feat: h5 desktop shell with sidebar and dark mode

- tokens.css/app.css: Miuix dual-color tokens + HyperOS 4 soft-glass rail
- bridge.js/router.js: Promise bridge wrapper + 5-page router with top clock
- index.html: sidebar + 5 page containers
- native wallpaper transparency: Theme.Hearth (showWallpaper + transparent window) + WebView transparent background

app/src/main/assets/h5/css/app.css

@@ -0,0 +1,61 @@
+/* Hearth 桌面样式：侧边栏 + 5 页框架 + 柔光玻璃容器 */
+/* Hearth launcher styles: sidebar + 5-page frame + soft-glass containers */
+
+* { margin: 0; padding: 0; box-sizing: border-box; }
+
+html, body { height: 100%; }
+
+/* 壁纸透明：html/body 不设背景，露出原生壁纸 */
+/* Wallpaper transparency: html/body keep transparent to reveal native wallpaper */
+html, body { background: transparent; }
+
+body {
+  color: var(--text);
+  font-family: -apple-system, "MiSans", "PingFang SC", sans-serif;
+  overflow: hidden;
+}
+
+.app { display: flex; height: 100vh; }
+
+/* 侧边栏：柔光玻璃容器，非纯色背景 */
+/* Sidebar: soft-glass container, not a solid color */
+.rail {
+  width: 80px;
+  background: var(--glass-bg);
+  backdrop-filter: blur(20px) saturate(1.2) brightness(1.05) contrast(1.1);
+  -webkit-backdrop-filter: blur(20px) saturate(1.2) brightness(1.05) contrast(1.1);
+  border-right: 1px solid var(--glass-border);
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  padding: 12px 0;
+  gap: 8px;
+  transition: width .2s;
+}
+
+.rail.expanded { width: 240px; align-items: stretch; padding: 12px 8px; }
+
+.rail-clock { font-size: 14px; color: var(--text-dim); display: none; }
+
+.rail-item {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  gap: 3px;
+  background: none;
+  border: none;
+  color: var(--text-dim);
+  padding: 8px;
+  border-radius: 16px;
+  cursor: pointer;
+}
+
+.rail-item .ico { font-size: 20px; }
+.rail-item .lbl { font-size: 11px; }
+
+.rail-item.active { background: var(--accent); color: #fff; }
+
+.content { flex: 1; overflow: hidden; }
+
+.page { display: none; height: 100%; }
+.page.active { display: flex; flex-direction: column; }